The present invention relates to carbon fiber chopped strands coated with resins and more particularly, to carbon fiber chopped strands coated with resins which can be suitably used for direct injection molding.
Carbon fiber-reinforced thermoplastic resins have been noticed in their high functions as well as high strength and high elasticity which are characteristics of carbon fibers and recently are being increasingly used as antistatic materials, EMI shielding materials utilizing their electrical conductivity and various sliding materials such as bearings utilizing their sliding properties.
Hitherto, moldings of the carbon fiber-reinforced thermoplastic resins have been generally produced by previously heating, melting and mixing carbon fiber chopped strands and thermoplastic resins using extruders to make them into injection moldable form, namely, to make pellets and then injection molding the pellets.
However, the above method has the problems that each of the carbon fiber chopped strands separates before the mixing step to cause deterioration of conveyability or meterability and the carbon fibers are cut short in the mixing step to cause deterioration in properties of the moldings.
Japanese Patent Kokoku (Post Exam Publn) No. 64-202 proposes a method in which carbon fiber chopped strands are previously coated with a thermosetting resin and the coated chopped strands per se are directly molded or a dryblend of the carbon fiber chopped strands with thermoplastic resin pellets are molded.
However, the materials used for ordinary molding receive a large impact force by vibration during pneumatic conveying or dryblending. When the fibrous materials in a dryblend are placed under such environment, they split and become cotton-like by separation or become powdery by crushing and as a result, the uniform blending state is lost. This also causes fluctuation in resin content or troubles in molding. Even when carbon fiber chopped strands coated with a thermosetting resin which are produced according to the method of the above-mentioned patent publication are mixed with a thermoplastic resin and directly molded, separation of the respective carbon fiber chopped strands before mixing step cannot be sufficiently prevented.